This invention relates to hydraulic control systems for automatic transmissions.
German Offenlegungsschrift No. 29 01 051 discloses a hydraulic control system for an automatic transmission in which electromagnetically operable pressure-control valves with flow-proportioning response are provided for the actuation of shift elements. In this way it is possible to use an electronic control device with a low cost transmission to control shifting into the forward or reverse or neutral transmission condition, depending upon the position of the pressure control valves. In its basic concept, the operation of transmission shift elements by electromagnetically operable valves in response to a central control unit is advantageous. When put into practice, however, the embodiment described in Offenlegungsschrift No. 29 01 051 would require an unreasonably large size for the hydraulic control system.